Over the past decade, there has been a lot of invention and improvement made for next generation high energy density rechargeable battery materials. High energy density rechargeable battery means the battery can hold and provide more energy compared to conventional lithium ion batteries of the same size, and therefore, cell phones will last longer and the driving range of electric vehicle will increase, making electric vehicles more practical and attractive.
Commercial lithium-ion batteries typically have a metal oxide based cathode, a graphite based anode, and a non-aqueous electrolyte. They exhibit a specific energy of ˜250 Wh/kg and energy density of ˜600 Wh/L. However, the current lithium-ion technology cannot satisfy the increasing energy density demands of the future. Lithium metal is an attractive anode material for rechargeable batteries as it offers the highest theoretical specific capacity of 3860 Ah/kg (vs. 370 mAh/g for graphite) and the lowest negative electrochemical potential (−3.04 V vs. SHE), of all metals. Substituting the graphite anode in lithium-ion batteries with metallic lithium can potentially enhance the overall energy density of the battery above 1000 Wh/L.
In a secondary battery utilizing a lithium anode, its electrolyte materials and compositions must show high cycling efficiency and safety in its electrolyte system to deliver high performance battery with long cycle life. In order to achieve high cycling efficiency of a cell, not only the electrolyte efficiency must be high, but also the electrochemical cell parts that is in contact with electrolyte must be electrochemically stable within the electrochemical testing voltage window to prevent any side reaction and degradation of the cell hardware or other cell components. Aluminum foils are used as the primary cathode current collector material in secondary lithium ion batteries over other metal foils due to its light weight, electrical conductivity, workability, and low cost of the material, and therefore new electrolyte materials should be both chemically and electrochemically stable within the battery charging and discharging voltage.